Lactones, phenolic aldehydes (such as vanillin), terpenes (essential oils) and wood tannins are all by-products of oak, so it is understandable that too much can rob a white wine of its fruit and delicacy.

In woody plants, carbon-based chemical compounds such as phenolics and terpenes comprise the main chemical defence.

Essential oils contain many terpenes, which are rapidly absorbed through the lungs and cross the blood-brain barrier.